On optimal power allocation and relay assignment in multiuser cognitive radio networks

This paper considers the problem of joint spectrum sensing and secondary data transmission in multiuser, multirelay cognitive radio networks. An optimization framework has been developed for the selection of source nodes, relay assignment and power allocation with an aim to maximize the sum throughput of secondary transmission under the constraints of sum transmission power for secondary source nodes, number of relays and probability of detection of primary user´s signal. A suboptimal scheme is then suggested to get rid of the high complexity of the optimal relay assignment scheme. Numerical results are presented to validate the proposed power allocation, optimal and sub-optimal relay assignment schemes for various values of probability of detection and total number of relays constraints.